Early versions of "presence" technology will appear on mobile phones later this year.
Motorola Inc., for instance, will begin tests next month of a system that will inform you ahead of time whether your sister has her phone turned on and, if so, whether she is on a call. That way, you'll know when to make the call, instead of guessing and trading voice mail messages all day.
Ultimately, the system should be offering data that discloses a cell phone user's geographic location, mood and availability. You may, for example, want to take only emergency calls from the office on weekends but all calls from family and friends.
Or you could choose to be informed that it's too early to call that friend who is vacationing in Hawaii, six hours behind New York.
Perhaps another friend will make it known that he's in a terrible mood and taking calls grudgingly. So this is not the time to tell him you're dating his ex-girlfriend.
"We see this evolving," said Craig Peddie, a Motorola general manager. "Presence will become an integral part of what you use your phone for."
To understand presence, start with the buddy lists made popular by America Online's instant messaging service. They tell you whether your friend or co-worker is online and ready to accept a quick note.
Add to that other devices and other attributes like availability. Calls and text messages may go to your cell phone when certain requirements are met and to your desktop computer or land-based phone otherwise.
Or consider this possibility: You're done with your workday and want to find friends who are nearby and available for a drink. Or perhaps even certain strangers, such as Yankee fans in South Boston.
In such cases, you have certain location and availability requirements. Presence can help you find people fitting set criteria. You can then call them or send text messages, depending on their stated preferences.
"Presence is about giving users control," said Lisa Pollock, director of messaging products at Yahoo! Inc. "By being able to convey whether or not you want to be contacted, and if so, how, senders of messages can then choose the method."
Such is the promise of presence that Microsoft Corp. is making it a core component of .NET, the company's next-generation initiative for providing information and services across the Internet and making it accessible on any device.
Later on, desk phones can be expected to have Net connections as well, so presence won't be limited a person's status on mobile devices. And if interactive television catches on, presence could migrate there, too.
"Parents can tell if the TV in the kids' bedroom is on (when they're supposed to be) finishing up their homework," said Leslie Daigle, co-chairwoman of an engineering working group that is developing standards to make presence work across platforms.
Bu presence also comes with risks. Stalkers and strangers may draw inferences from your status.
Because of such concerns, the University of Michigan last month curtailed an early Internet technology called Finger, which reveals such information as location and the time someone logs on. Now, the service is accessible only from terminals on campus, and location is dropped.
"Sentiment has been shifting," said Seth Meyer, a systems engineer at the university. "Society is really revisiting its decisions to make information available at a certain ease."
Companies developing presence services promise that the features will be opt-in: A friend or a co-worker will need your permission to get your presence information.
But Richard Smith, chief technology officer for the Privacy Foundation, wonders about the protections when a spouse buys their partner a cell phone, or a parent buys one for a kid. Or for that matter, what about a company issuing phones for all employees?
"You could set up a phone to report their position without them knowing it," he said.
Tim Connolly, director of mobile applications at Ericsson, said the wireless industry is well aware of the concerns and understands the need to make users feel secure.
"Any lapses or situations where users are feeling their privacy is being compromised is detrimental to the entire industry," Connolly said.
Just as it took time to get accustomed to screening calls with caller ID, comfort with presence won't come right away.
Mark McDowell, president of Invertix Corp., a presence software company, believes the public will readily accept on-off status, given familiarity with Internet buddy lists.
"As to people publishing their availability and updating that several times a day, that's going to take time," he said.
It'll also take social engineering, said Ken Smiley, an analyst with Giga Information Group. He notes that a phone may remain on while it sits idle in a car, confusing callers who equate "on" with "available."
Customers will have to remember to turn phones off when leaving them alone.
So far, PresenceWorks and Yahoo have incorporated presence with address books, while Dynamicsoft's software can automatically schedule conference calls when everybody's available at once.
Tests of Motorola's services are expected to begin next month in unspecified markets. Initially, customers will be limited to knowing whether a phone is on or busy. Location information will come next year.
Ericsson has software for desktop computers that lets you direct incoming text and Internet voice messages to the device of your choice, depending on whether you're busy, offline, away or unavailable. Similar software is being programmed into Ericsson's mobile phones.
Microsoft's .NET expects to analyze your past behavior and online calendars to figure out where and when to best reach you and how to prioritize incoming missives.
The system may notice that you tend to read messages abut online auctions first, so it'll try harder to deliver them next time, and could even interrupt you in a meeting. But it won't interrupt you if your calendar says you're meeting with your boss about a raise.
"The real power we think is decoupling the presence network from the buddy lists," said Charles Fitzgerald, director of Microsoft's .NET platform strategy. "By knowing where you are, it's a lot easier to build more interesting, more personalized solutions."
© MMI The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed